نشریه فناوری اطلاعات و ارتباطات ایران
سال پنجم شماره 15 (بهار و تابستان 1392)

In this paper, the role of radiation elements in the performance of reflect array antenna is studied, and each element is designed and simulated and the phase response is compared. Also, the relations needed for designing reflect array antenna are discussed and one sample reflect array antenna is designed in the KU band and the results are presented.

In this paper a robust controller using µ-synthesis method has been designed for attitude control system of a micro-satellite in LEO orbit. Then the controller has been evaluated with accurate linear and nonlinear simulations. After necessary evaluation three-axis stabilization method with only magnetic torques and auxiliary gravity gradient boom was been selected. Nonlinear kinematics and dynamics equation of this system was obtained and linearization was performed on it. Finally the system was converted into a multivariable linear time varying system and controller for this system was performed via µ-synthesis, which has been done by changing from time varying system into system with uncertainty.

In a research, that this paper reflects its results, a model for stating the relationship between investment in IT and customer satisfaction was developed. This study starts with extensive literature review on investment in IT and customer satisfaction. Then, a conceptual model with four criteria (including Economic, educational, diffusion of ICT and telecommunication) and one latent variable (indicator of customer satisfaction) were designed. This model’s primary validity was approved through expert opinion. Then, in a field study in the organization under study, the required data have been gathered for testing functional approval of the model. In the next stage of research, by using SEM techniques and interactive regression equation in the form of path analysis and using the software like SPSS and LISREL, we concentrated the factors of relationship between latent variable and observed variables. The finding of the research shows direct relationship between economic and educational factors of IT investment on customer satisfaction.

Increasing data throughput of Multipath time-varying HF channel by employing decision feedback equalization is addressed. In this paper, we propose multichannel FQRD-RLS adaptive filtering algorithm employing weight extraction in Decision-directed mode. A comparison between this technique and IQRD-RLS algorithm is performed. Simulation is conducted under channel parameters with respect to MIL-STD-188-110B. The results show higher data throughput in a frame with acceptable computational cost. It is also shown that the achieved data throughput is as same as using MC-FQRD-RLS algorithm in Full-Iteration equalization mode, at a much lower computational cost.

In this paper a Model Predictive Method based controller is proposed to control a satellite. Model Predictive Control (MPC) has been well known as a practical control method for various systems in industry. A problem with this method is its computational effort and time consuming. To reduce computational load Laguerre functions have been proposed in this literature. Simulation results are given to show feasibility and the validity of the design. A comparison between the time consumed in the presence and the absence of the Laguerre functions is done too.

Finding algorithms for the diverse issues proposed in Computational Geometry including pseudo-triangulation of point set is among the scientific subjects, which has already attracted the attention of computer scientists'.A pseudo-triangle is a simple polygon in the plane with exactly three convex vertices, called corners. Three reflex chains of edges join the corners. A pseudo-triangulation for point set is a partition of the convex hull of point set into pseudo-triangles whose vertex set is point set.Many possible optimality criteria have been investigated for pseudo-triangulations which are often based on edge weights or angles in which computing a minimum weight pseudo-triangulation for a point set is among the open problems. A pseudo-triangulation is called minimum if it consists of exactly n-2 pseudo-triangles and the minimum number of edges needed for it is 2n-3. Every vertex of a minimum pseudo-triangulation is pointed. A vertex is pointed if it has an incident angle greater than π.With respect to the proposed cases, the aim of this thesis is to present new methods for pseudo-triangulation of point set in the plane, so that it can open new algorithmic reflections in this field. This research shows that the generation of convex hull layers for point set and their pseudo-triangulation, using two new algorithms which have been considered in this research, minimizes pseudo-triangulation. Also a new algorithm has been considered to generate spiral simple polygon such that the generation of random simple polygons has two main areas of application: testing the correctness and evaluating the CPU-time consumption of algorithms that operate on polygons.